Hemodialysis, generally called simply dialysis, is a method for permanently maintaining patients whose kidneys have failed to function totally or almost totally because of disease or injury.
In healthy kidneys, blood flows through the kidney tubes where waste materials pass through the microscopically thin walls and are eliminated through the urine, while the cleansed and purified blood returns into circulation. Hemodialysis duplicates this process almost exactly. A dialysis machine is connected to an artery via an intake tube and the natural pumping action of the heart drives the blood into the machine, where it is passed through a semi-permeable membrane immersed in a specially prepared cleansing solution. The blood is then returned to the patient's body through another tube to a vein.
In most cases, where a person requires dialysis on a regular basis, a simple operation is performed, whereby a vein in the arm is connected to an artery. This creates a vein which is rich in arterial blood. The connecting tube is called a "shunt".
In order to perform the dialysis it is common to insert into the shunt, a hypodermic needle connected to a tube that leads to the dialysis machine. Between the metal part of the hypodermic needle and the tube is a plastic butterfly-wing shaped connection (hereinafter called "butterfly"). This enables easy insertion and removal of the needle.
The common practice is to insert the second needle for the return flow of the blood from the dialysis machine to the vein, close to the point of entry of the first needle (approximately 5 to 10 cm apart).
When the needle is removed from the shunt, blood spurts out due to the fact that the shunt is filled with arterial blood which is driven by pressure from the pumping action of the heart. To eliminate this spurting of blood, one has to exert pressure at the point of entry of the needle into the skin. This is done by pressing a sponge on the area. The sponge is usually a gauze ball or folded gauze pad and is held in place by pressing with a finger. The blood flow is stopped and the needle removed. The pressure is maintained on the skin, on the blood vessel and on the shunt below it until the shunt is closed by a blood clot and a clot forms on the skin--a process which can take from 5 to 30 minutes, depending on the individual patient. When the clots are formed, the sponge is removed and replaced with a clean dressing.
From the moment that the needle is removed until the end of the pressure process, the nurse/attendant must hold the sponge in place, and cannot release the pressure, thus taking valuable time which could be used to attend to another patient. The nurse/attendant is naturally impatient to complete the process, and may release the pressure on the sponge too early, to see if the blood has clotted. This results in uneven pressure being applied on the area which is unhealthy. When pressure is released before the proper time, blood clots are not properly formed and each further burst of blood enlarges the former clot. The shunt eventually becomes blocked by these excess clots and may have to be replaced.
There exist several methods for preventing blood spurting from the entry/exit point of the needle.
One such method involes applying a plastic (non-permeable) adhesive tape which contains in its center an expandable sponge pad to one side of the needle. The pad is positioned above the point of entry/exit of the needle and expands on contact with fluids. Pressure is exerted on the sponge pad under which lies the needle and the needle is removed by holding the butterfly on the needle. Continuous pressure is exerted on the sponge whilst the other half of the adhesive tape is adhered over the wound. Digital pressure continues until the shunt and the wound are dry. The pressure on the sponge is released and the patient is free to leave with the dressing adhered. Alternatively, when the nurse/attendant assumes that the hole in the shunt and the wound has healed, pressure is released. We are unaware of any system whereby the entire adhesive tape is adhered to the wound before the needle is removed. We have experimented and have found that in the presently used adhesive tapes the glue sticks to the needle and to the butterfly, which makes it difficult to remove the needle with ease, especially while a finger is exerting pressure on the center of the sponge (this is in fact an uneven pressure which may cause blood spurts).
Another method for preventing blood spurting is as follows:
A folded gauze sponge is placed above the needle. The needle is removed and instead of exerting digital pressure, one of the undermentioned methods is used:
a) An elastic bandage is rolled around the arm, creating pressure. This system is unsafe and is rarely used.
b) A mechanical clamp is applied on the gauze sponge. The clamp is similar to tongs whose curved arms are held together by a spring. These tongs replace the finger when the needle is removed and the nurse/attendant is free to attend to other patients. This is an expensive method--the life-span of the tongs is short because the spring does not last long. Risks of cross infection are prevalent because the tongs are re-usable.
c) A plastic arm strap is placed over the gauze sponge. The arm strap has a rough, notched surface along its underside with a ratchet device at one end, allowing the strap to be pulled through it in one direction. Attached to the ratchet device is a shoulder-shaped housing which fits over the sponge. The shoulders create pressure on the sponge and replace the previously used finger. The needle is removed by means of the butterfly and extra pressure is exerted by tightening the strap for a time period of between 5 to 30 minutes, depending on the patient. The strap is removed by means of a release clip on the ratchet.
There are several disadvantages in using this latter system.
First of all the arm strap acts like a belt, creating homogeneous pressure all around, on the sponge and around the entire arm. This may stop the free flow of venous blood, causing the arm to turn blue due to lack of sufficient blood supply. Secondly, the sponge and/or the shoulder shaped housing may slip from the exact spot where pressure is required. Moreover, in this method, when the sponge with the absorbed blood is removed, the entire dried clot attached to the sponge is pulled off, which may cause the wound to bleed again. Therefore, after the removal of the sponge, a new adhesive tape with a new sponge has to be placed on the wound.
The above described arm strap cannot be used with the adhesive tape having an expandable sponge as previously described, for the following reasons:
a) Because of its shape the strap does not exert pressure directly on the sponge beneath the adhesive tape.
b) The shoulder-shaped housing of the arm strap is shaped to fit over an ordinary gauze sponge and would slip on the smooth surface of the adhesive tape when the strap is tightened. It therefore does not facilitate steady pressure at the point of entry/exit of the needle.
c) The system whereby half the adhesive tape is adhered at first, and the second half only after removal of the needle, does not permit the use of the above arm strap together with known adhesive tapes.
d) The arm strap slips from the center of the pad whilst the needle is removed and insufficient pressure results in spurting of arterial blood.